Project: Evaluating the Efficacy of Physical Habitat Modification to Reduce the Impacts of M. cerebralis Infection in Streams

Primary Investigator: Kevin Thompson
Project Summary: Areas on two streams were physically modified to reduce aquatic worm habitat. Another area was chosen as an unmodified control site for comparison. The investigators looked for before-versus-after changes in the density of aquatic worms, parasite spores produced from aquatic worm samples, numbers of floating parasite spores in water samples downstream of the changed sites, and the percentage of brown trout infected with the parasite. At one treated site there was a reduction in floating parasite spore numbers in flowing water for a year, but the aquatic worm population came back quickly in the good worm habitat that remained after construction. At the other site, there was a reduction in aquatic worm numbers for at least a year, but there was no decrease in the number of floating parasite spores in flowing water downstream of the site. At both sites, aquatic worm samples collected after the habitat changes and held in buckets overnight in a lab produced the floating parasite spores, indicating that infected aquatic worms were still there. Not enough time has passed to test brown trout of the proper age for changes in the percentage of infection. More exploratory sampling upstream and downstream of both treated sites for aquatic worms showed that there were other, smaller worm habitats that contained infected worms. Therefore, although monitoring of the brown trout population will continue to see if changes occur in the percentage of fish infected, initial indications are that small-scale habitat manipulations such as used in this study might not be very successful in changing the percentage of fish infected over an entire stretch of a stream.
Funding Period: 2002-2003
Final Report: Thompson_02-03.pdf
Dataset(s) associated with this project:

There are no datasets associated with this project.